Methods and apparatuses for the treatment of glaucoma using visible and infrared ultrashort laser pulses

ABSTRACT

Transcorneal and fiberoptic laser delivery systems and methods for the treatment of eye diseases wherein energy is delivered by wavelengths transparent to the cornea to effect target tissues in the eye for the control of intraocular pressure in diseases such as glaucoma by delivery systems both external to and within ocular tissues. External delivery may be effected under gonioscopic control. Internal delivery may be controlled endoscopically or fiberoptically, both systems utilizing femtosecond laser energy to excise ocular tissue. The femtosecond light energy is delivered to the target tissues to be treated to effect precisely controlled photodisruption to enable portals for the outflow of aqueous fluid in the case of glaucoma in a manner which minimizes target tissue healing responses, inflammation and scarring.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation and claims the benefit of U.S.nonprovisional application Ser. No. 13/464,949, filed May 4, 2012, whichclaims the benefit of U.S. provisional application No. 61/484,824, filedMay 5, 2011, both of which are hereby incorporated by reference in theirentireties.

FIELD OF THE INVENTION

The present invention pertains generally to methods and procedures foruse in ophthalmic surgery. More particularly, the present inventionpertains to the use of laser devises for photodisruption of tissue inthe eye. The present invention is particularly, but not exclusively,useful for an ophthalmic surgical procedure involving transcorneal orfiberoptic photodisruption of tissue of the corneo scleral angle as atreatment for glaucoma.

BACKGROUND OF THE INVENTION

Glaucoma refers to a series of relatively common eye disorders in whichpressure within the eye is sufficiently high as to result in damage tosensitive intraocular structures, including the retina and optic nerve.Glaucomas are classified as primary (including chronic open angleglaucoma, angle closure glaucoma, mixed mechanism glaucoma and infantileglaucoma and secondary (related to other diseases of the eye). Theelevation of intraocular pressure ultimately leads to irreversibledestruction of the optic nerve. The clinical symptoms, which are notreadily recognized in the early stages, are characterized mainly by aslow, relentless, progressive narrowing of the field of vision, anddecrement in visual integration processing, including diminished darkadaptation. In the absence of treatment, the eventual outcome is totalloss of vision often accompanied by severe eye pain.

In order to fully appreciate the described embodiments, a brief overviewof the anatomy of the eye is provided. As schematically shown in FIG. 1,the outer layer of the eye includes a sclera 17 that serves as asupporting framework for the eye. The front of the sclera includes acornea 15, a transparent tissue that enables light to enter the eye. Ananterior chamber 7 is located between the cornea 15 and the crystallinelens 4. The anterior chamber 7 contains a constantly flowing clear fluidcalled aqueous humor 1. The crystalline lens 4 is connected to the eyeby fiber zonules, which are connected to the cilliary body 3. In theanterior chamber 7, an iris 19 encircles the outer perimeter of the lens4 and includes a pupil 5 at its center. The diameter of the pupil 5controls the amount of light passing through the lens 4 to the retina 8.A posterior chamber 2 is located between the crystalline lens 4 and theretina 8.

As shown in FIG. 2, the anatomy of the eye also includes a trabecularmeshwork 9, a narrow band of spongy tissue within the eye that encirclesthe iris 19. The trabecular meshwork (“TM”) varies in shape and ismicroscopic in size. It is generally triangular in cross-section,varying in thickness from about 100 μm to 200 μm. It is made up ofdifferent fibrous layers, having micro-sized pores forming fluidpathways for the egress of aqueous humor from the anterior chamber. Thetrabecular meshwork 9 has been measured to a thickness of about 100 μmat its anterior edge, Schwalbe's line, 18 at the approximate juncture ofcornea 15 and sclera 17.

The trabecular meshwork widens to about 200 μm at its base where it andthe iris 19 attach to the scleral spur. The passageway through the poresin the trabecular meshwork 9 lead through a very thin, porous tissuecalled the juxtacanalicular trabecular meshwork 13, which in turn abutsthe interior side of a structure called Schlemm's canal 11. Schlemm'scanal 11 is filled with a mixture of aqueous humor and blood componentsand branches off into collector channels 12 that drain the aqueous humorinto the venous system. Because aqueous humor is continuously producedby the eye, any obstruction in the trabecular meshwork, thejuxtacanalicular trabecular meshwork or Schlemm's canal, prevents theaqueous humor from readily escaping from the anterior chamber. Thisresults in an elevation of intraocular pressure in the eye. Increasedintraocular pressure can lead to damage of the optic nerve and eventualblindness.

Present surgical techniques to lower intraocular pressure includeprocedures enabling fluid to drain from within the eye to extra ocularsites. However, these drainage or “filtering” procedures not onlyincrease the risk of causing a lens cataract, but often fail by virtueof their closure resulting from the healing of the very wound createdfor gaining access to the surgical site. Ab inferno surgical procedures,also, if not adequately stealth eventually fail. In creating the egressby photoablation or by photodisruption less inflammation at the egresssite is induced than by current techniques, thus prolonging filtrationwound function.

Lasers were first used in 1965 to repair retinal detachments. Theprocedure involved chorioretinal coagulation in which a laser beampositioned from without the eye was used to achieve fusion of the retinaand the choroid. The technique consisted of introducing a laser beamfrom outside the cornea, and by employing the refractive media of theeye itself, the laser radiation was directed in such a manner that itwas concentrated at a selected point upon the retina/choroid so that thetissues in a very localized area were photothermally congealed.

In contrast to thermal energy produced by visible and by infraredlasers, such as Nd:YAG systems, the high photon energies of femtosecondlasers can photodisrupt the material in question, namely eye tissue, ina manner which does not cause significant target tissue temperatureelevation. By photodisruption, both visible and infrared femtosecondlaser radiation can be used to drastically alter the target tissue in a“cold” environment. This becomes significant for controlled removal oforganic substances, such as living tissue, in contradistinction totreatments in which heat is generated, e.g. by thermal lasers, whichcould damage, if not destroy, delicate eye tissue adjacent to the targetsites to be removed and thereby induce healing responses.

Femtosecond (“FS”) lasers used for this purpose include the group ofrapidly pulsed lasers which emit at 0.4 to 2.5 μm in the visible andinfrared spectra. In contrast to the thermal visible and infraredradiation from some Nd:YAG or CO₂ lasers or the like, the high energyphotons from femtosecond lasers at photodisruptive fluence levels areabsorbed by the target tissues. This absorption creates a hot plasma atthe focus, vaporizing tissue. The plasma subsequently expandssupersonically launching a pressure wave. Later, a cavitation bubbleforms and eventually collapses. The extent of the tissue damage causedby the pressure wave and cavitation bubble expansion isenergy-dependent. Femtosecond pulses deposit very little energy whilestill causing breakdown, therefore producing surgical photodisruptionwhile minimizing collateral damage.

Juhasz T, Chai D, Chaudhary G, et al.; Application of Femtosecond LaserSurgery for the Treatment of Glaucoma; in Frontiers in Optics, OSATechnical Digest (CD) (Optical Society of America, 2008) disclosed thatFS laser pulses could be used to create partial thickness scleralchannels that drain aqueous humor into the sub-conjunctival space,showing potential for the treatment of glaucoma. Toyran S, Liu Y, SinghaS., et al.

Femtosecond laser photodisruption of human trabecular meshwork: an invitro study; Exp. Eye Res. 2005; 81(3); 298-305, disclosed the use of FSlasers to perform photodisruption of human TM strips ex vivo, creatingfull-thickness ablation channels through the TM without collateraldamage. The ideal settings for creating lesions with minimal collateralside effects on the inner surface of the TM are: Ti:Sapphire laser beam(45 fsec, 1 kHz, 800 nm) with 14.4 mJ pulse energy and an exposure timeof 0.5 sec Nakamura H, Liu Y, Witt TE, et al.; Femtosecond laserphotodisruption of primate trabecular meshwork: an ex vivo study;Invest. Ophthalmol. Vis. Sci. 2009; 1198-204 disclosed photodisruptionby FS laser of the TM of ex vivo, intact, enucleated human and babooneyes. The settings were 45 fsec, 1 kHz, 800 nm with 60 to 480 μJ and0.001 to 0.3 sec exposure time. The study showed that laser ablation ofthe TM ab interno in ex vivo primate eyes is feasible by a customfemtoseeond laser ablation system with a gonioscopic lens. Thephotodisruption did not reach Schlemm's canal, although this goal couldeasily be achieved through an alteration in laser settings and deliverymethods.

However, successful use of ultrashort laser pulses, such as thoseproduced by a FS laser, in vivo to produce channels in the TM to relieveglaucoma has not been demonstrated by the work discussed above andpresents challenges not present in those experimental studies. Inparticular, the laser beam must be delivered to a precise location onthe TM in such a way as to avoid damage to adjacent and interveningtissue. The challenges of delivering adequate photodisruptive energy inprecise patterns in shapes and depths include (a) the curved surface ofthe target, (b) the target lies beyond the critical angle of visibleocular structures seen through the cornea unaided, (c) optical couplingsystems are necessary to visualize and target the intended treatmentsites, e.g. trabecular meshwork and Schlemm's canal, (d) the location ofSchlemm's canal may be difficult to establish particularly as it liesbehind the optically significant trabecular meshwork, (e) once the innerwall of Schlemm's canal therefore the “blood aqueous bather”, ispenetrated, blood components may obscure the optical pathway for anyfuture optical viewing and/or treating beams.

SUMMARY OF THE INVENTION

The present disclosure provides for the delivery of photodisruptivefluence levels of visible or infrared photons to the precise point ofthe target tissue of the eye by direct or fiberoptic delivery systemswithout impinging upon the overlying or surrounding tissue or upon thetissue at the region of beam entry into the eye for the purpose ofeffecting removal of select tissue in precise shapes and depths.Ulltrashort laser pulses are directed into the eye either through thecornea or ab internally via fibers to enable laser radiation, includingvisible and infrared radiation, under gonioscopic control or throughfiberoptic elements, including fiber lasers, thereby effecting preciselycontrolled photodisruptive removal of such target tissue of the corneoscleral angle. Such tissue may include TM, juxtacanalicular TM, andportions of Schlemm's canal, collector channels, aqueous veins andsclera. Preferably, a laser with pulse duration in the range from 20 fsto 300 ps is used, although it is to be recognized that even shorterpulse durations may be used. The laser uses an optical coupling toaffect controlled photodisruption of the target

It is to be understood that this summary is provided as a means forgenerally determining what follows in the drawings and detaileddescription, and is not intended to limit the scope of the invention.The foregoing and other objects, features and advantages of theinvention will be readily understood upon consideration of the followingdetailed description taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary of this disclosure as well as the followingdetailed descriptions of the embodiments is further understood when readin conjunction with the accompanying drawings, which are included by wayof example, and not by way of limitation with regard to this disclosure.

FIG. 1 is a schematic sectional view of an eye illustrating the interioranatomical structure.

FIG. 2 is a perspective fragmentary view of the anatomy within theanterior chamber of an eye, depicting the corneoscleral angle

FIG. 3 is a schematic sectional view of an eye illustrating afiber-optic probe disposed next to the trabecular meshwork in theanterior chamber of the eye.

FIG. 4 is a schematic sectional view of an eye with an attached indirectgoniolens with an interior mirror. The goniolens is attached to thecornea via suction or mechanical devices.

FIG. 5 is a schematic sectional view of an eye with an attached directgoniolens with an external mirror system. The mirror and lens areattached via retaining systems to the sclera.

FIG. 6 is a schematic sectional view of an eye with an attached indirectgoniolens with an interior mirror. The goniolens is attached to thesclera via suction or mechanical devices.

FIG. 7 is a fragmentary cross section of the anatomy within the anteriorchamber of an eye, showing a segment of target tissue to bephotodisrupted.

DETAILED DESCRIPTION EMBODIMENTS OF THE INVENTION

The present disclosure provides for the delivery of photodisruptivefluence levels of visible or infrared photons to the precise point ofthe target tissue of the eye by direct or fiberoptic delivery systemswithout impinging upon the overlying or surrounding tissue or upon thetissue at the region of beam entry into the eye for the purpose ofeffecting removal of select tissue in precise shapes and depths.Ultrashort laser pulses are directed into the eye either through thecornea or ab internally via fibers to enable laser radiation, includingvisible and infrared radiation, under gonioscopic control or throughfiberoptic elements, including fiber lasers, thereby effecting preciselycontrolled photodisruptive removal of such target tissue of the corneoscleral angle. Such tissue may include TM, juxtacanalicular TM, andportions of Schlemm's canal, collector channels, aqueous veins andsclera. Preferably, a laser with pulse duration in the range from 20 fsto 300 ps is used, although it is to be recognized that even shorterpulse durations may be used. The laser uses an optical coupling toaffect controlled photodisruption of the target

A coupling system employs a goniolens or an ab interno fiberoptic thatprecisely targets the outflow obstructing tissues to effect removal ofthe outflow obstruction. Such targeting may include localization ofSchlemm's canal, detected optically or otherwise, such as by OCT(optical coherence tomography) or photoaccoustic spectroscopy.

The optical system may also include features to enhance visualization ofSchlemm's canal by controlling localized and diffuse pressure gradients,for example by creating relative hypotomy to induce blood reflux intoSchlemm's canal. Means of coupling the globe of the eye optically to thelaser beam delivery system may be included to enable the exquisiteprecision of the photodisruptive laser. Such systems include goniolensflange systems, including coupling capabilities such as suction, withdiameters in the range of 10 to 25 mm, fluidic chambers both to controlintraocular pressure (“IOP”) and to maintain corneal clarity and shape.To enable optical pathways, such as planar surface to enable precisiontargeting, suction means for similar purposes which, in addition,exquisitely control light energy delivery registration to the targettissues. In the case of the fiber laser, the fiber may have multiplechannels to control intraocular pressure, to enable visualization andoptical coupling to Schlemm's canal.

Preferably, the procedure for creating openings in the trabecularmeshwork comprises:

-   (1) imaging the target tissue, (2) locking a pattern to the    image, (3) creating the pattern and controlling the depth of laser    penetration, and (4) maintaining IOP to enable visualization of    Schlemm's canal and concurrently controlling egress of blood to    prevent optical decoupling of light obstruction for subsequent laser    delivery to target tissue.

Several 20 to 200 μm partial depth openings may be created concurrentlywithout complete penetration to prevent blood reflux or other opticalpathway obscuring elements after which Schlemm's canal inner wallpenetration is effected to all sites concurrently.

IOP is altered to affect this optical pathway, which is lowered to allowtargeting of Schlemm's canal then elevated to prevent blood reflux.

Gonioscopic and fiberoptic delivery systems for laser surgery in the eyewherein thermal and/or radiation damage to the eye is minimized aredisclosed.

In connection with glaucoma treatment, laser energy is appliedgonioscopicay transcorneal or directed through the fiberoptic element.When gonioscopic, the deflecting mirror may be stationary or may haveelements to adjust the mirror within the goniolens delivery system bothto precisely target the subject tissue and to precisely directfemtosecond laser energy to these tissues. Such a mirror may bemechanically controllable to effect scanning. The gonioscope is coupledto the eye by various means, including prongs, clips, suction,viscoelastic, aqueous solution and inflatable balloons. The laserdelivery system is also coupled both to the goniolens and via thegoniolens to the target cornea-scleral angle tissues. The opticaldelivery is stabilized through precise control of the goniolens andgoniolens mirror position and control of the femtosecond laser energydelivered to the target tissue by sensors which detect precise lasertissue interactions as they occur.

The systems may include image stabilization to enable precise lasercoupling to the docked goniolens device which includes a mirroring/lightdeflecting system to enable viewing and treating the cameo scleral anglestructure at the laser delivery system, at the goniolens or fiber orboth.

In one emboidment a goniolens is applied to the cornea and a laser beamis focused on the target tissue. In another embodiment, a fiberoptichandpiece is passed through an incision in the eye where it isstabilized and secured to the globe and the laser beam is focused on thetarget tissue.

In one goniolens configuration, a multidimensional mobile reflectivesurface (e.g., a Mylar balloon) is moved (horizontally, vertical and indepth) by inflation or deflation. This system can include fluidics tocontrol temperature within the lens system. This configuration also mayinclude concurrent illuminating beams and treatment beams with imagecapture for pixel to pixel image matching to control precise targetingwhen coupled to a mobile or curved target.

In another goniolens configuration DLP (Digital Light Processing)optical semiconductors or equivalent are used to control the gonioscopicdelivery.

In yet another configuration, the system is capable of detecting cardiaccycle pulsation and the filling and emptying causing choroid translationof outflow structures by optical or ultrasound techniques, coupling thedetection system to the optical delivery system to enable precise photodisruption of target tissue by means of a combination or individually:(a) mechanically controlled mirror, (b) piezoelectric controlled mirror,(c) DLP optical semiconductor, (d) surface reflecting fluid balloons(e.g. Mylar) included at the laser and/or within a gonioscopic deliverysystem.

The goniolens air/surface optics are either plano or concave or convex.The mirror/light reflecting element optics are either plano, concave,convex, complex curved or in a segmented mirror array. Light alteringmaterials include variable optical density fluid lair filled balloons,glass, plastic or metal shaped to enable photodisruption to occur attarget regions which are both beyond the critical angle to the cornealsurface and are curved, residing on the inner surface of a globe.

The laser beam emitted from the laser source may be parallel, convergentor divergent and it is altered by the lens mirror system to enable allforms of emitted beams to focus with a suprathreshold photodisruptivefluence at the target tissue.

In one configuration, the goniolens includes a pressure detection meansto compensate for cardiac cycle translation of the entire globe/orbitstructures/choroid and intraocular structures including detection ofchoroidal filling and emptying from cardiac cycle events, which mayinclude pressure detectors in the goniolens or goniolens flange andsoftware in the laser delivery system to compensate for this targettranslation to enable precise target photodisruption on the movingtarget.

A concentric ring system may be used to enable (1) registration eitherthrough suction or through a retaining mechanical device (prongs,corkscrew) (2) IOP control (3) ocular pulsation detection.

A bladder/balloon system may be used to control optical surfaces,including cornea and any internal mirroring surfaces to enable anemitter to best couple to the target tissue. In coupling the cornea, thecornea may be compressed (e.g. flattened) or the goniolens cornealsurface may be curved and coupled to the corneal surface by opticallyneutral fluidic means, liquids and gels.

In the case of a direct (e.g. non mirror) goniolens delivery system thedirect goniolens is retained in a holding device coupled to an opticdelivery system with mirror external to the goniolens. Such externalmirroring enables the laser source and viewing optics to be inclined atangles from 10° to 170°, often 60° to 120° and most often 80° to 110° inrelation to the target tissue.

In the moving eye/goniolens complex the laser fires only when the targetis optically captured and stabilized. These optical coupling mechanismsenable precise photodisruption at the target tissue in space and indepth.

In the case of an ab interno fiber, the optical delivery is stabilizedthrough precise control of the fiber position and control of thefemtosecond laser energy delivered from the fiber tip by sensors whichdetect precise fiber tip position and alignment to the target tissue.

The photodisruptive radiation is directed to the target tissues, namelycorneoscleral angle structures comprising trabecular meshwork,juxtacanalicular trabecular meshwork, components of Schlemm's canal, andin some cases adjacent cornea, sclera, and iris structures to createfluid passageways between the anterior chamber of the eye and Schlemm'scanal or alternatively the suprascleral/subTenon space or alternativelythe suprachoroidal space.

Photodisruptive laser energy is targeted to gonioscleral anglestructures for the purpose of removing tissue which impedes aqueousoutflow or to redirect outflow. Openings are created by patterns ofadjacent photodisruption regions in this tissue. The patterns consist ofvarious shapes in size ranging from surface dimensions of 20 to 200microns and depth adequate to penetrate the inner wall of Schlemm'scanal. Patterning enables openings to be created individually,sequentially or several concurrently. In one iteration, whenconcurrently, the depth is controlled at each opening to allow thecreation of craters without entering SC until all craters are at a depthafter which minimal additional tissue removal would enter SC thusenabling the optical pathway in the anterior chamber to remain clear.Only at this time would SC be perforated at each crater concurrently tominimize optical pathway obscuration by blood reflux from SC.

In other iterations, in which the IOP is regulated to prevent bloodreflux from SC, other patterning options are used, to create individualopenings or several concurrent openings in from 1 to 12 clock hours ofthe angle.

Surgical trauma to the outer wall of Schlemm's canal, or in the case offull thickness penetration to the overlying conjunctival and Tenon'stissue, all extremely subject to scarring, is thereby minimized. This isin contrast to current procedures which result in more scarring ofsensitive ocular structures and therefore more rapid failure ofprocedures whose purpose is to control IOP.

By minimizing trauma while creating an aqueous humor egress route, thepresent invention minimizes healing and increases longevity of improvedoutflow at the site of filtration. The present invention enables asignificantly greater opportunity for success, including the ability totitrate the amount of photodisruptive energy necessary to result in ameasured lowering of intraocular pressure.

Referring to FIG. 3, an overview of a method of operating a fiber-opticlaser delivery system for treatment of glaucoma or other eye conditionsfollows: FIG. 3 is a side sectional view of the interior anatomy of ahuman eye showing fiber-optic probe 23 in relation to an embodiment of amethod of treating glaucoma. After applying local and/or peri- orretro-bular anesthesia, a small self sealing incision 14 can be createdin the cornea 15 with a surgical blade or femtosecond laser or otherdevice. The anterior chamber can be further stabilized with aviscoelastic agent. Fiber optic probe 23 can then be positioned andadvanced through the incision 14 into the anterior chamber 7 to targetthe trabecular meshwork immediately or ab interno or a distal end offiber-optic probe 23 contacts or is substantially adjacent to the targettissue for removal. Fiber optic probe 23 may be manually directed orheld rigid in relation to the ocular structures via anchoring to theglobe, sclera 17 or cornea 15 through devices which may include prongs56, which devices also may hold in place a pressure regulating system 55and an ocular pulse sensing system 54.

Laser energy is delivered from the distal end of fiber-optic probe 23targeting the trabecular meshwork across the anterior chamber or incontact or adjacent to the tissues sufficient to cause photodisruption.Tissues to be removed include the trabecular meshwork 9, thejuxtacanalicular trabecular meshwork 13 and an inner wall of Schlemm'scanal 11. Fiber-optic probe 23 delivered photodisruptive energy createsan aperture in the proximal inner wall of Schlemm's canal 11 but doesnot perforate the distal outer wall. In some embodiments, additionalapertures can be created in the trabecular meshwork and the targettissue following reposition of the probe. Thus by removing outflowobstructing tissues, the resultant aperture or apertures are effectiveto restore relatively normal rates of drainage of aqueous humor.

Referring to FIGS. 4-6, an overview of a method of surgical gonioscopicdelivery systems for the treatment of glaucoma or other eye conditionsfollows: FIG. 4 shows an optical delivery system consisting of anindirect goniolens 50 attached to the sclera 17 mechanically or byprongs 56 or suction, with an internal mirror 52. The mirror may beindividual or segmented and fixed or mobile to enable scanning for bothviewing and for treatment targeting. In the condition of a mobilemirror/mirror surface, the mirror 52 can be controlled mechanically orpneumatically or with a Mylar type surface reflecting balloon. Themirror can be plano, concave, convex and singular or in a segmentedarray.

A beam 51 of pulsed radiation is generated by a femtosecond laser anddelivered into the eye by the delivery system, including the goniolens50. The beam 51 is reflected by a mirror 52 which may be controlled by aservo system 53 connected to a controller 58 to focus scanningphotodisruptive energy onto the curved surface of the target tissue. Theoptics enable bidirectional use, one direction is used to treat thetarget tissue, the other direction is used to view and/or sense the x,y, z coordinates of the targeted tissue to enable precise treatment andremoval of the target regions. The beam 51 has a set of pulse parameterranges specifically selected to photodisrupt targeted tissue of thetrabecular meshwork, while minimizing damage to surrounding tissue.Thus, the beam has a wavelength between 0.4 and 2.5 microns. The exactwavelength used for a particular subject depends on tradeoffs betweenstrong absorption by the meshwork and transmission of preceding ocularstructures and aqueous humor. FIG. 4 shows an indirect goniolens 50attached to the cornea 15 mechanically 56 or by suction with an internalmirror 52. FIG. 5 shows a direct goniolens attached to the sclera 17 bysuction 57 or mechanically with a mirror system 52 external to thegoniolens.

The pulse duration of the laser beam is chosen to have a highprobability of photodisrupting material of the corneoscleral angleoutflow tissues. There is an inverse relationship between the laserpulse duration and the energy required in each pulse to generate opticalbreakdown. The pulse duration is selected to be shorter than the thermalrelaxation of the target so that only the targeted material is heatedand the surrounding tissue is unaffected. Thus, the pulse duration isbetween 20 fs and 300 ps. The pulse rate is between 1 and 500 KHz

The pulse energy is chosen to facilitate photodisruption and minimizethe shockwave effect of the laser light. A typical value for the pulseenergy is between 300 to 1500 nJ.

The spot diameter is chosen such that sufficient laser energy density isprovided to facilitate photodisruption of the trabecular meshworktissue. The spot size is between 1 to 10 microns.

The goniolens 50 is anchored either on the sclera 17 or the cornea 15 bya suction ring 57 or prongs 56. The anchoring system is attached to apressure regulating system 55 and an ocular pulse sensing system 54. Theanchoring system is either concentric or segmented. Scanning the spot inthe x,y, and z direction effects patterns for tissue removal.

FIG. 7 shows the target tissue to be photodisrupted in a perspectiveview 70 and in a cross sectional view 71. In this case a single site isdemonstrated but understood is duplication of this site over severalregions individually or concurrently.

Alternatively, the TM may be approached ab externo via thesemi-transparent sclera using high numerical aperture optics and afundamental wavelength that allows deep penetration through the sclera.This produces targeted ablation of the deep corneo scleral anglestructures, specifically targeting TM, JCTM and portions of Schlemm'sCanal. In this instance the coupling lens could be planar or curved.

All coupling lenses, goniolenses and fibers require focusing devices atthe laser which couple optically to the lenses, goniolenses and fibersto effect appropriate fluences at the target tissue to effect microablations and thereby tissue removal.

Preferably, the procedure for ultrashort laser pulse trabeculostomycomprises the steps that follow.

-   -   1. Prepare patient for femto laser trabeculostomy procedure.    -   2. Prepare femto laser which has been pretested on a model of        trabecular meshwork for accuracy and fluence at the target        tissue.    -   3. Align gonio lens with optical alignment system of laser        visualization system to target planned trabecular meshwork        tissue sites and lock the target into the system for treatment.    -   4. In the case where the gonio lens mirror is not stationary,        but mobile, assure the tracking system is engaged to control all        optical surfaces.    -   5. Secure the gonio lens onto the eye. This may be pneumatic or        physical engagement to control all movement and enable tracking        system to engage and apply energy only when target is precisely        focused for appropriate delivery of laser energy to the target        sites. If mobile, laser will only engage when precise target        alignment assures exact tissue targeting in x, y and z loci.    -   6. Anchor the gonio lens either on the cornea or the sclera        either by prongs or a suction ring.    -   7. Attach anchoring system to a pressure regulating system and        an ocular pulse sensing system.    -   8. In the ease where cardiac cyclic translation of target is        monitored and controlled, engage this system to enable precise        depth targeting.    -   9. Couple end of optical pathway to a femto second laser.    -   10. Locate Schlemm's canal with the gonioscope.    -   11. The goniolens mirror may be curved to allow targeting of        curved trabecular meshwork.    -   12. Focus laser beam on target tissue.    -   13. Photodisrupt target tissue until crater forms adjacent to        Schlemm's canal.    -   14. Repeat step 14. up to 10 times in a pattern, for example,        from 5 o'clock to 1 o'clock.    -   15. The patterns consist of various shapes in size ranging from        surface dimensions of 20 to 200 microns and depth adequate to        penetrate the inner wall of Schlemm's canal.    -   16. Using the laser, concurrently extend craters so they become        ostia into Schlemm's canal.    -   17. Detach gonioscope.    -   18. In the case where femto laser energy is delivered        fiberoptically within the eye, all above apply. In addition,        following paracentesis and stabilization of the anterior chamber        with aqueous and/or viscoelastic agents, the fiberoptic delivery        system is placed into the anterior chamber and imaging of all        relevant structures is performed to assure targeting to planned        sites. The fiber and fiber position maintaining devices are        engaged and enabled, manually and/or automatically

The terms and expressions which have been employed in the foregoingspecification are used therein as terms of description and not oflimitation, and there is no intention, in the use of such terms andexpressions, to exclude equivalents of the features shown and describedor portions thereof, it being recognized that the scope of the inventionis defined and limited only by the claims that follow.

The invention claimed is:
 1. A method of creating a plurality ofopenings in a trabecular meshwork of a patient's eye to conduct fluidfrom an anterior chamber into a Schlemm's canal of the eye, comprising:ablating a first crater to a first depth in the trabecular meshworkadjacent to the Schlemm's canal with first laser pulses without enteringthe Schlemm's canal; ablating a second crater to a second depth in thetrabecular meshwork adjacent to the Schlemm's canal with second laserpulses without entering the Schlemm's canal; extending the first craterwith third laser pulses to a third depth and extending the second craterwith fourth laser pulses to a fourth depth, wherein the first crater isextended to the third depth and the second crater is extended to thefourth depth after the second crater has been extended to the seconddepth, so as to penetrate an inner wall of the Schlemm's Canal, to formthe plurality of openings to conduct fluid from the anterior chamber tothe Schlemm's canal, and to decrease optical pathway obscuration byblood reflux from the Schlemm's canal; and wherein each of thefemtosecond laser pulses comprises a wavelength of within a range from0.4 to 2.5 microns, a fluence level to produce optical breakdown, and apulse duration in a range from 20 femtoseconds to 300 picoseconds. 2.The method of claim 1, wherein the laser pulses are directed through acornea of the eye to ablate the trabecular meshwork.
 3. The method ofclaim 1, wherein a gonioscopic lens is coupled to the eye and the laserpulses are transmitted through the gonioscopic lens.
 4. The method ofclaim 1, wherein the laser pulses are scanned in an ablation pattern ofadjacent regions in the trabecular meshwork to form each of a pluralityof craters, the plurality of craters comprising the first crater and thesecond crater, the pattern in the trabecular meshwork comprising asurface dimension within a range from 20 to 200 microns.
 5. The methodof claim 4, wherein the plurality of craters is formed concurrently andwherein of the plurality of craters is subsequently extended to enterSchlemm's canal and to form the plurality of openings.
 6. The method ofclaim 1, wherein the laser pulses are reflected off a curved mirror andwherein the laser pulses are scanned and focused into a curvedtrabecular meshwork to form the plurality of openings in the curvedtrabecular meshwork.
 7. The method of claim 1, wherein an intraocularpressure of the eye is lowered to allow targeting Schlemm's canal andthen elevated to prevent blood reflux.
 8. The method of claim 1, whereinSchlemm's canal is detected optically or by optical coherence tomography(OCT) or by photoaccoustic spectroscopy.
 9. The method of claim 1,wherein the laser pulses are directed through a sclera of the eye toablate the trabecular meshwork.
 10. The method of claim 1, wherein anintraocular pressure of the eye is lowered to allow targeting ofSchlemm's canal.
 11. The method of claim 1, wherein an intraocularpressure of the eye is elevated to prevent blood reflux.
 12. The methodof claim 1, wherein the laser pulses are reflected off a flat mirror toform the plurality of openings in the trabecular meshwork.